Study examines rice photosynthesis

Hybrid plants typically yield more per acre than the average of their parent lines or a variety check. That advantage is attributed to hybrid heterosis, but understanding just what contributes to this advantage may help plant breeders make even greater strides in developing more efficient crops.

“We want to know what makes hybrids tick,” said Dr. Ted Wilson, director, Texas AgriLife Research and Extension Center in Beaumont. Wilson, discussing ongoing research during a recent field day, said breeding hybrid rice[2] has been part of the station’s efforts for years, but new technology and new techniques may help scientists understand the “morphological, physiological, and genetic attributes that collectively provide this heterotic advantage.”

Wilson and others are working with growth chambers that measure canopy photosynthetic rates. A snorkel pipe rises above the canopy to “get a real measure of carbon dioxide. We measure the amount of carbon dioxide entering and leaving the chambers every five minutes. The difference between the two equals plant growth.”

He said research measures how light penetrates the plant canopy. “Plants that are better at capturing sunlight will grow better. Some hybrids capture 30 percent more than inbreds. They produce a bigger plant.”

He said the system is set up to measure 20 chambers at a time. “So we can check 20 varieties at the same time. During each sampling, photosynthesis in each chamber is measured for up to 72 hours, providing photosynthesis measurements for a range of temperature and light intensities.

“After the chambers are removed, light is measured above and below the canopy of each variety every hour from 8:30 a.m. to 4:30 p.m. At maturity of main and ratoon crops, grain yield is estimated.”

Wilson said two-thirds of all the hybrids produced are worse than the inbred varieties. “Those get thrown away.”

He said the hybrid studies complement inbred breeding programs and help identify which inbreds perform best.